Under Decree 98/2014, for the first time, the Government introduces a detailed regulations on setting up communist party cell and trade union bodies within a private company in Vietnam including foreign-invested enterprise. In particular,

A company with at least three communist party members who have an employment term of 12 months or more must establish its own communist party cell. Before Decree 98/2014, these employees can participate in other communist party cells.
The local communist party will be entitled to help setting up a communist party cell within a private company including companies which have no communist party member. A private company must facilitate the establishment of a communist party cell within such company.
A company with at least five trade union members or employees who want to join trade union must set up its own trade union within 6 months from the date of establishment. If the company fails to do so, the local trade union organisation will appoint a temporary trade union body to represent the employees in such company. It is not clear if a company with less than five trade union members or employees who want to join trade union will also need to have a temporary trade union body appointed by the local trade union organization.

Vietnam Business Law